Advantage of sex in terms of genetic variation and rate of evolution

Advantage of sex in terms of genetic variation and rate of evolution

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Advantage of sex in terms of genetic variation and rate of evolution. Consider two loci, A and B and new mutations to alleles a and b which can interact to produce a genotype of high fitness in a novel environment. . Since mutations are rare originally the only new chromosomes in the population will be Ab (from a B -> b mutation ) and aB (from an A -> a mutation). An asexually reproducing stain would have to wait for the second mutation because it has no way of reassembling the existing alleles into new combinations. The sexual strain could produce the high fitness genotype much faster by recombination (see figure 11.1 page 286). This advantageous effect of recombination would be reduced in small populations because the number of mutations occurring is the product of mutation rate and
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Unformatted text preview: population size, so the advantage of sex and recombination would be reduced in small populations. These two observations suggest that sex might evolve by group selection : we have 1) genetically isolated "groups" (sexual and parthenogenetic strains), 2) disadvantage to the individual and 3) advantageous to the long-term survival of the group. But G. C. Williams notes that the cases of facultative parthenogens (species that can reproduce either parthenogenetically or sexually) strongly suggest that there must be some short-term advantage to sex (otherwise it would be selected out of population as a strategy; note that we are dealing with the same group here so the advantage of sex at the group level does not apply). Some possible advantages:...
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